Relay contact resistance
I’ve been using a. wireless Tado to switch an Ecodan ASHP off if the house temperature gets too hot. The switching circuit is a 12v 1mA supply which needs shorting to turn off the heat pump. This is done by the Tado relay. This has worked well for over a year but now the heat pump will not turn off. I suspect the relay contacts have got oxidised and do not self clean with only 1mA current. Any ideas to make the contacts self clean under these low standing currents?